Determining hemoglobin (Hb) concentrations is often useful in diagnosis and treatment of patients. For example, Hb concentrations are useful in diagnosing whether a person is anemic. Several techniques currently exist for determining serum hemoglobin. For example, techniques include phlebotomy (puncturing a vein and drawing blood) with subsequent laboratory analysis of the drawn blood, microscopic assessment of mucous membranes, and subjective assessment of conjunctiva color and clinical parameters. By far the most widely used technique is phlebotomy followed by analysis with a flow cytometer. This technique is reliable, but uses one or more technicians, an expensive piece of equipment (the cytometer), and typically a centralized location for the analysis due to the cost of the cytometer. Another technique uses magnification and analysis of blood flow through mucous membranes.